This invention generally relates to a piston for a monotube shock absorber that includes a tortuous outer band providing a bearing surface.
Monotube shock absorbers include a single tube defining an inner chamber that slidably receives a piston assembly connected to a rod. The piston assembly separates the inner chamber into a compression side and a rebound side. One type of piston assembly utilizes a “pod” piston. The pod piston includes a cylindrical body having a first surface facing the compression side and a second surface facing the rebound side. A plurality of inner ports is formed within the cylindrical body to allow fluid to flow between the compression and rebound sides. Valve discs are supported on the first and second surfaces to control fluid flow between the compression and rebound sides.
In a traditional pod piston design, a plurality of pods is formed on each of the first and second surfaces. Each pod forms a raised surface and is spaced apart from each adjacent pod by a recessed area. The pods provide tuning areas that facilitate blow-off. Tuning areas can be configured to control damping characteristics and blow-off as needed to help compensate for pressure build-ups. The pods are located in areas where pressure has a tendency to build-up.
Some disadvantages with this traditional pod piston design include limited area available for increasing the size of blow-off areas, and the unavailability of an adjustable preload. One solution to these problems involves using an annular piston configuration. An annular piston has a cylindrical body having a first annular land facing the compression side and a second annular land facing the rebound side. The annular piston has a larger blow-off area that is provided by the first and second annular lands.
A disadvantage with a traditional annular piston design is that it is often difficult to redirect fluid flow between compression and rebound sides of the annular piston. Redirection of fluid is typically from an outer circumferential area on one land to an inner circumferential area on the other land. Annular pistons have taken on various different configurations in an attempt to solve this problem. Examples of these annular pistons include cross-drilled pistons, double-piece pistons, and clash-tooled pistons. Each of these configurations requires time consuming machining and/or processing steps to provide flow passages between compression and rebound lands, which is expensive.
For the above reasons, it would be desirable provide an annular piston assembly for a monotube shock absorber that provides a larger blow-off area, and which provides a simplified and more cost effective configuration for controlling fluid flow between rebound and compression sides of the annular piston assembly.